490 



Fishery Bulletin 97(3). 1999 



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each of the years in which spawner 

 abundance falls below the proposed 

 threshold, there was a serious recruit- 

 ment failure, depressing the age-1 

 population. In the case of spawn-year 

 1984, two year-class failures in a row 

 were evident. All of the very low year 

 classes shown in Figure 8 coincide 

 with high April SLH the prior year 

 (Table 1), suggesting that most low 

 spawner abundances were largely the 

 result of environmental forcing and a 

 strong recruitment-stock relationship. 

 Two of the years shown, 1984 and 1993, 

 followed the major El Niiio southern 

 oscillation (ENSO) events of 1982-83 

 and 1992-93, and likely resulted from 

 the rise in sea levels and accelerated 

 northward currents often associated 

 with these events and their likely influ- 

 ence on conditions in April ( Huyer et al., 

 1979; Chelton and Davis, 1982; Chelton 

 et al., 1982; Huyer and Smith, 1985). 



However, the data suggest that the fishery does 

 play some role in creating the low spawner abun- 

 dances shown in Figure 8. Although the low recruit- 

 ment in 1990 corresponds to a poor spring transition 

 in 1989 (Table 1), the data suggest that the high har- 

 vest of egg-bearing females in April of 1989 exacerbated 

 this recruitment failure (Fig. 2; Tables 1 and 2), subse- 



Age-1 recruits 



Age-1 catch (April-July) 



1980 



1985 1990 



Year of age-1 recruitment 



1995 



Figure 7 



Age-1 ocean shrimp recruitment index, calculated assuming elemental trawl 

 efficiency of 0.50. and the portion of the index for the April-July catch of 

 age-1 shrimp, by year, 1980-96. 



quently depressing spawner abundance (Fig. 8). The 

 large difference between age-1 recruitment and the 

 age-1 component of the spawner index in 1993 (Fig. 

 8) also suggests that spawner abundance may have 

 been depressed by the fishery in that year. The close 

 association between a year-class failure and low 

 spawning abundance the same year also demon- 



